Hire an architect.

You'll save the most by doing it right the first time.

If you're going to have soil testing performed and consult with an engineer on site, it would be best to include the other members of your team (designer/architect and builder) so everyone is on the same page.

Are you concerned that you may find gigantic rocks on your home site? Your contractor should be able to refer you to engineers. Or ask neighbors in houses nearby who they used for consultation, especially if the lot drainage affects other people's property.

I'm not really worried about any large rocks. We are in Mississippi and out in the country, so no neighbors around to ask.
My biggest concern is that it will be more complicated and expensive to build less square footage and I don't want to get too far into the design without addressing it.

I agree with Charles Ross as to having everyone on the same page. As for 1/2 basement versus whole basement foundation the extra cost is minimal I have a walkout that has about a bit less than 1/2 underground we use it for the staircase and a ton of great storage and work shop where windows and doors really don’t matter . We have a media room , games room , exercise space and a large office in the part where the windows and doors are I love this space and in the summer a nice cool spot to be.

What's the grade difference from the front wall of the house to the back wall?

Normally with sloped lots, the house is designed to not be too deep perpendicular to the slope and is lengthened parallel to the slope so to minimize the vertical fall across the depth of the house. The phrase "we've selected a lake style floor plan" leads me to believe what you've "selected" may not be the best fit for the site.

But good luck with your build. Exciting times ahead!

We have a full walk out foundation but not all of it is finished. We have 2 bedrooms, office, exercise area and full bath. We have an unfinished part which has our air handlers, tankless water heater, well pump, slop sink, extra fridge and freezer and shelving for household supplies. We also store things such as christmas tree and decorations. I can't imagine not having the unfinished area. We do not have an attic.

I'm with vinmarks. Even with an attic, extra space in the basement always comes in handy and you'll want it plumbed for a bathroom.

Basements do not have to be completely finished. As others have noted above, many have unfinished areas. How much is finished is up to you. Main floors, however, generally must be finished or else the homeowner will not be happy/satisfied living in a partially completed space. The incremental cost of making the basement go from half foot print to full footprint is not substantial compared to the rest of the home build. You will find this out if you need to have your potential new home appraised for financial purposes - the basement, unless fully finished and at the same level as the rest of the home, will contribute substantially less to the overall appraised value of the home, even though it makes up half of the total square footage. It probably more depends on what the real meaning of "a little extra space" is to you. Best wishes on your new build! Fun times ahead!

I think a basement, half or full will be a cool place in Mississippi in the summer. Good luck with your new build.

Do you own the lot? I lived in Vicksburg for 5 years and that soil there was sandy. Anyway, you would be best served to hire a good local architect who is familiar with the ground and specific topography and can guide you on avoiding mistakes at this crucial stage. Good luck.

@architectrunnerguy the slope is approximately 2.5%. What is the best slope for something like a lake style home?

You're right when I say "we've selected and I understand what we want may not work for the lot, and will be talking to architects to determine the best style home for the land. If this style of home is not best suited for the lot we will just sell the land and build elsewhere.

@FloMagan We do own the lot. Actually it's 12 acres and we are living on the property while we build. We are in thr Golden Triangle area so the sand from the River isn't such a concern, at least according to the soils maps I've reviewed. I appreciate the advice about hiring a pro to help guide us and that is our plan moving forward.

@live_wire_oak I thought of that as well. I've spoken to a few builder friends who have built basements in the past in this area and as long as we have the runoff under control they said we shouldn't have any problems.

What is a lake style house...?

Here is what we're looking at....

I’m in Los Angeles and live in a hilly area and our house is like that. The bottom floor is smaller than top main floor, but this is mainly due the natural slope and size of land (land is $$$ out here). I think only you know what size house fits your needs or wants. For me, that would be too big of a house, but then there is only 3 of us.

2.5% slope is a mild slope for a single level that requires 5% slope away from the house for drainage. Maybe you're at 25% slope? With a 40' deep house, the rear level would be 10' lower, or enough for a walk out. Typically our walk out levels are built about 1/2 the size of the main level to take advantage wild minimizing excess mass grading and retaining walls, keeping the costs from escalating too much.

@JeffreyRGrenz Yes, that was a typo. 25% slope

Nice inspiration house. Hope you achieve the look you want.

More single story space will likely tax higher than adding a basement and/or a steep enough roof for additional attic storage. Personally, I'd consider a full waterproofed concrete block "basement" even if half ended up being "cellar" and only half were to be finished. The labor and blocks for three extra concrete block walls with footing/foundation up to code will add to the cost.

Your inspiration pic has a retaining wall ... so ... you're expecting to need one on each side of the house because of the width of the sloped area?

Are you planning this year and intending to build next spring ... or sooner?

Especially in a rural area, consider doing some of the major landscaping well before you begin building. Begin with getting the major grading done such as what you will need to create the embankment for at least a 6' high retaining wall (that will separate your finished basement from the dirt of your "cellar" -- that ground below that part of the house with no basement) and grade to enable the retaining wall to extend on both the right and left side of the house at least eight feet beyond the exterior side walls of the house and any side porches and/or side deck.

You could go ahead and have any major grading done above and below the embankment / retaining wall so you have the level and sloped areas you want/need in order to have the rainwater flow away from your home -- even go ahead and create your driveway and sow the grass so any parts of your yard you don't need to have dug up for the house itself and/or utilities, etc., will have a head start.

As you plan your landscaping, remember that you can have the retaining wall include steps built into it on one or both sides. If you're building a half basement, you may well want the retaining wall beneath the house to also separate the dirt cellar embankment from the rear interior basement wall.

Let us know how your project is going.

@suezbell that is a good point about taxes, I didn’t think of that! That's why I came to this forum!!!

I am fully expecting to need retaining walls on at least a portion of the build.

We plan to break ground next year some time... COVID has the exact date in the air.

We plan to break ground well before we would like to start the build, we may try to do some of it ourselves depending on what the architect and engineer says. My husband has access to some heavy machinery.

Thanks for the support and feedback!

We have a very similar slope and are in sand & silt soil. Our house is built somewhat diagonal to the slope though so our SW corner is walkout w/ the rest below grade. We built near the top of our slope so we've about a 4% grade upslope of our house and 24% downslope from the back.

First make sure you have a good Architect or designer, a good engineer and a good landscape architect or site planner. They are worth the cost. You will get a lot more for your money w/ a good design.

For drainage and keeping your basement dry I'm guessing that your key thing is to get stormwater and roof runoff from the upslope side around the house to the downslope side without compromising the integrity of the hillside or your house. This is typically not difficult but must be done correctly and is typically designed by the landscape architect or site planner though some engineers will do it.

Under the category of for what it's worth...

I've actually lived in two different residences with a back deck high off the ground and no other access than thru the house -- planned that way for security and privacy issues. While that set up does keep the dogs off the deck, canines are about the only animals it truly discourages -- and a gate could do that. Cats and wildlife, including snakes, find a way up to take in some sun on the deck and raii, especially if there is a shade tree nearby.

As you consider your plan, along with considering the amount of direct sunlight (south, east, west in the northern hemisphere) that your home will receive, consider its use and access. A back porch or deck might be more accessible and practical if you wrap at least a boardwalk/deck around the side for another access point and, in the event of an emergency, a possible fire escape.

Something you might consider depending upon the orientation (N,S,E,W) and the slope of the land might be a split level plan -- but keep in mind the heat/ac costs of that.

If this is to be your forever home, you may want to consider an "L" shaped home with one wing being your master bedroom suite and great room and necessities -- perhaps a mud room with multiple purposes: back entry from a porch or carport or garage, a deep washer/dryer/ironing board closet, a vac & cleaning product closet and, closest to the kitchen, plenty of floor to ceiling shelving as pantry.

Having the other wing of an "L" shaped home -- or a "T" shaped home or even a "U" shaped home -- with doors between the main living area and the "extra" space so you can close off that space when not needed could be an energy saver ... and not just with regard to heat/ac: unused space could be closed off and not need cleaning as frequently.

There are a lot of floor plan magazines in the magazine sections of big box stores so flip through some and consider all your options so you can make an informed decision.

If this is your forever home -- if you expect to live in it as you age -- consider beginning your plan by first considering what you need when arthritis is affecting your knees and ability to access the home and any stairs in it.

As you consider your building site on a large tract of land, especially, if you're having a plat created, also consider the possibility that you might need a mortgage and, if so, consider whether or not you might want/need to sell a part of the land ... perhaps to a family member (children) for building their home nearby.